My ongoing project car

[N.RotaryTech]

Originally Posted by NoDOHC

I don't like the shape of that port. This design is giving up significant low end without making any improvements in the high end because that port has about a 15 degree later port close, but it is at such an awkward angle that it will not help chamber charging at high speeds.

Nice text-book reply.

Originally Posted by NoDOHC

For what it is worth, I made 138 WHp on a bone-stock s4 6-port block, factory ECU, modified AFM (lean the mix up a little) and stock exhaust. Stock intake manifold too. This doesn't bode well for the porting on your engine that made 14 Hp more stock than mine. (What I am thinking is that the port design is actually hurting your power.)

Nice.
I suppose that this porting might be hurting the performance.

Let me just say this: with the S5 motor I had in there, It pulled from 3.5k-6.5k rpm but just runs out right at 7k.
Redlines at 8k. Buzzer at 8500. Rev limiter at 9k.

With the HBP motor I have in there, it really opens up around 5.5k rpm and wants to keep going at 7k rpm. But some of the last times I drove it, it bogs down after 7k rpm, probably for some reason being with the stock ecu.

I just know there was and is a big difference in performance with this HBP motor compared with the S5 motor. I can feel it.

I love this HBP motor and wouldn't go back.

Now for the decision of if I should stick with the stock port center iron that's in the HBP motor, or if I should swap with this ported S5 center iron.
It would probably depend on the whole debate of if ported center irons increase or decrease power, etc.
Stock ported center irons would probably be better, but I'm going with the ported iron just to see what happens.
Ive already experienced the stock center iron with this HBP motor.
Why not see what its like with a ported center iron.
This is a bridge ported motor, so I'm not really too concerned with the low-end performance anyway.

Anyway this is what the end irons already look like.



With this rebuild I'm just going to clean up the ports.
But mainly this rebuild is about putting new o-rings and gaskets in.